The structure of the major glycoprotein from avian myeloblastosis virus is studied in order to understand its interactions with the cell surface. Analysis is made of the role of the viral glycoproteins in the behavior of transformed cells and its interactions with specific cellular receptors. Avian myeloblastosis virus glycoprotein is isolated and its structure determined by chemical and physicochemical methods. The physiological effects of the viral glycoprotein on the glucose transport and glycolysis are evaluated. Different cleavage products are used to characterize the cellular receptors for the glycoprotein.